This invention Pertains to compositions which have improved abrasion resistance and comprise per 100 weight parts of a thermoplastic material or resin an impact modifier in amount greater than 20 weight parts, preferably greater than 30 weight parts, more preferably greater than 50 weight parts, and especially about 100 to 500 weight parts. The impact modifiers have Shore A hardness of greater than 40, preferably greater than 60, more preferably greater than 70, and especially greater than 80. This invention pertains to the use of rigid, semi-rigid, and flexible thermoplastic materials, with and without plasticizers. The improved abrasion resistance of the compositions herein is less than 0.20 gram loss, preferably less than 0.15 gram loss, when flexible and semi-rigid thermoplastic elastomers are used in the compositions of this invention and less than 0.250 gram loss, preferably less than 0.220 gram loss, when rigid thermoplastic materials are used. Abrasion herein is measured by the Taber Abrasion Method.
Rigid thermoplastic materials, such as polyvinyl chloride resins, generally contain less than about 10 weight parts of a plasticizer per 100 weight parts of the resin. Semi-rigid thermoplastic materials generally contain about 10 to 30 weight parts of a plasticizer per 100 weight parts resin. Flexible thermoplastic materials generally contain greater than 30 weight parts of a plasticizer per 100 weight parts resin. In terms of Shore A hardness, the rigid thermoplastic materials are considered to have a hardness of greater than about 90, semi-rigid thermoplastic materials have a hardness of about 80-90, and flexible thermoplastic materials have a hardness of less than about 80.
Thermoplastic elastomers are not completely cured or vulcanized and can be readily processed and reprocessed on conventional processing equipment. The reprocessability of thermoplastic elastomers compared to conventional elastomers which are thermoset results in a great reduction in loss due to scrap, with consequent economic benefit to the processor. A variety of thermoplastic elastomers have been introduced which include thermoplastic elastomeric polyesters, styrene block copolymers, and thermoplastic olefin-rubber blends. Typical of such materials are the styrene-butadiene-styrene block copolymers sold as Kraton.RTM. brand thermoplastic elastomers by Shell Chemical and Hytrel.RTM. brand polyesters sold by DuPont. Many of these thermoplastic elastomers have found applications in consumer goods such as in industrial applications such as in wire coating, hose and tubing, electrical connectors, and automotive parts.
U.S. Pat. No. 4,659,766 discloses compositions which allegedly have good solvent resistance, abrasion and compression set characteristics. Such compositions comprise 70 to 30 weight parts high rubber ABS graft copolymers, 30 to 70 weight parts polyvinyl chloride resin, and 45 to 65 weight parts plasticizers used for plasticizing polyvinyl chloride resin. Amount of plasticizers given in this patent is based on the sum of the ABS graft copolymer and polyvinyl choride resin. This equates to a minimum of 64 weight parts of the plasticizer per 100 weight parts of the polyvinyl chloride resin. The large amount of the plasticizer indicates that the polyvinyl chloride product is of the flexible type.
Japanese patent application 60-148,408, published Jan. 19, 1987, discloses flexible and semi-rigid compositions comprising 100 weight parts polyvinyl chloride resin having average polymerization of at least 2000, 20 to 200 weight parts ABS resin and a partially crosslinked acrylonitrile/butadiene copolymer, and 20 to 300 weight parts of a plasticizer composed of a linear alkyl ester of trimellitic acid. The compositions disclosed by this reference have excellent flexibility, heat resistance, cold resistance, and mechanical strength.
A companion case was refiled recently as a CIP for the same three inventors as herein, covering the compositions containing impact modifiers exclusively with vinyl chloride-acrylate copolymers as thermoplastic materials. In that companion case, the claimed compositions are believed to have exceptional low temperature properties. The parent case was filed Sep. 9, 1988 and bears Serial No. 242,394, and is entitled "Very Soft, Flexible, Plasticized Polyvinyl Chloride Compositions."
In the case Ser. No. 242,395 filed Sep. 9, 1988, and entitled "Flexible Blend Compositions Based On Overpolymers of Vinyl Chloride Polymers On Ethylene Copolymers", an invention is described which pertains to the addition of a plasticizing agent to an overpolymer produced by overpolymerizing vinyl chloride-based polymer onto an ethylene-based polymeric substrate. The resulting blends have improved oil swell and low temperature properties.